Liquid column gravity meter



Sept. 29, 1936. BRYAN 2,055,479

' LIQUID COLUMN GRAVITY METER Original Filed Oct. 8, 1932 Ar/bm/ 5 5mm ea Patented Sept. 29, 1936 UNITED STATES LIQUID COLUMN GRAVITY METER Andrew B. Bryan, Tulsa, Okla., assignor to Standan! Oil Development Company, a corporation of Delaware Application October 8, 1932, Serial No. 636,790

Renewed January 16, 1936 2 Claims. (Cl. 265-1) This invention relates to improvements in liquid column gravity meters and more particularly .relates to the cancellation of temperature effects in liquid column gravity meters.

The invention will be fully understoodfrom the following description taken in connection with the accompanying drawing in which latter the figure is a side elevational view of a preferred form of apparatus.

Referring particularly to the drawing, an upright tubular vessel is shown in the form of a U, the legs of which are designated l and 2. A suitable liquid 3 such as mercury is disposed within the U shaped vessel. A closed bulb or reservoir 6 opens into the leg 2. A body of gas 1 is disposed within the reservoir 6 and the upper portion of the leg 2. The column of mercury in the leg 2 is partially displaced and supported by the body of gas I which extends into the leg 2. The column of mercury has an upper surface 9 in the leg 2 and an upper surface I0 in the leg I. The surface 9 is at a lower level than the surface it) and the body of gas I is maintained under the pressure exerted by the portion of the column of mercury in leg I above the level 9.

The upper end of the leg I is closed at H forming a chamber l2 at the upper end of the leg 1. Changes in gravity are observed as changes in the vertical distances between the liquid levels 9 and I0.

Changes in temperature of the atmosphere surrounding the apparatus above described cause changes in the dimensions of the apparatus, the density of the liquid 3 and the pressure of the gas 1. Changes in the pressure of the gas I are the most serious source of error.

Error is compensated for by the following arrangement of parts: The chamber I2 and the upper portion of the leg I extend within the bulb or reservoir 6. A small amount of a suitable compensating liquid, such as carbon tetrachloride, chloroform, carbon bisulphide or the like, is disposed in the chamber I 2 above the level of mercury at In. With the type of instrument used only a small drop of compensating liquid is necessary. There is thus a downward pressure exerted at III which is produced by the saturated vapor pressure of the compensating liquid and which has a rate of change with the temperature which depends only on the .compensating liquid used. The rate'of change with temperature of the gas pressure at the surface 9 is directly proportional to the gas pressure and can be made to have any value by adjusting the gas pressure. It is thus possible by adjusting the gas pressure in the reservoir 6 to reach a state where the gas pressure at 9 and the vapor pressure at [0 change with temperature at the same rate, and when this adjustment has been made a change in temperature will produce no motion of the liquid column. In other words, it is possible to adjust the gas pressure in the reservoir 6 until the combined effect of temperature changes on the gas pressure at 9, the dimensionsof the apparatus, the density of the liquid column 3 and the vapor pressure of the compensating liquid is zero for certain ranges. The gas reservoir 6 is caused to surround that portion of the apparatus containing the compensating liquid in order that the gas and compensating liquid may always be at the same temperature. While the compensating liquid has been described as contained within the chamber I2 above the mercury column, it will be understood that it can be contained in a separate vessel in communication with the chamber above the mercury. The chamber above the mercury need not necessarily be evacuated. It could contain air or any other gas at low pressure.

Various changes may be made within the scope of the appended claims in which it is desired to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

1. A liquid column gravity meter comprising a closed system including an upright tubular vessel containing an upright column of mercury, a chamber containing a body of compensating liquid opening upon and exerting pressure upon the upper end of the column, the pressure being substantially entirely due to vapor pressure of the compensating liquid pressure, a chamber containing a body of gas engaging the other end of the column under pressure such that the gas pressure changes with temperature at the same rate as the vapor pressure of the compensating liquid whereby the mercury column is motionless upon change in temperature of the system.

2. A liquid column gravity meter comprising a closed system including an upright tubular vessel containing an upright column of mercury, a chamber containing a body of compensating liquid opening upon and exerting pressure upon the upper end of the column by its saturated vapor pressure, a chamber containing a body of gas supporting the lower end of the column under pressure such that the gas pressure changes with temperature at the same rate as the vapor pressure of the compensating liquid whereby the mercury column is motionless upon change in temperature.

ANDREW l3. BRYAN. 

